MATLAB: How to get the estimated coordinates when applying affine transform

image processing

How can I get the estimated or adjusted points when apply affine transformation with control points matched from distorted image (input_points)and original image (base_points)? Example points like below:

base_points= [202.5 198.5; 3998.5 198.5; 4002.5 2602.5; 202.5 2602.5];

input_points= [278.5 246.5; 4038.5 170.5; 4162.5 2702.5; 170.5 2622.5];

t_affine = cp2tform(input_points,base_points,'affine');

Can I get the estimated coordinates using imtransform like below?

estimate_aff = imtransform(input_points,t_affine);

Best Answer

Use TFORMFWD.

Related Solutions

MATLAB: How to transform given XY coordinates using ‘lwm’ tform

A forward version of the lwm transform is not provided because it is not guaranteed to be a 1-1 transformation, but perhaps it would be useful to you simply to do the inverse fit

tform_inv = fitgeotrans(img2_coordinates, img1_coordinates, 'lwm', 10);

and then apply transformPointsInverse.

MATLAB: How to display registered images on top of one another

This enhancement has been incorporated in Release 14 Service Pack 2 (R14SP2). For previous product releases, please read below for any possible workarounds:

The reason that the images are not aligned is because the x and y data of the images do not correspond with each other. In other words, the images do not share a common spatial coordinate system.

To correct this, you must explicitly specify the x and y coordinates of the images. The following example shows how to specify these values when you apply the transformation using IMTRANSFORM.

% Construct the transform.
tform = cp2tform(input_points, base_points, 'projective');
% Apply the transform, using the IMTRANSFORM syntax that  
% returns the x and y values.
[registered, xdata, ydata] = imtransform(unreg, tform, 'Fill', 255);
% Display the combined figure, specifying the x and y coordinates.
figure, imshow(registered, 'XData', xdata, 'YData', ydata);
hold on
h = imshow(base);
set(h, 'AlphaData', 0.5);
title('Registered+Base image');

Best Answer

Related Solutions

MATLAB: How to transform given XY coordinates using ‘lwm’ tform

MATLAB: How to display registered images on top of one another

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